Tone activated alert receivers are well known and are regularly used by emergency agencies including fire, police, ambulance and rescue services. The National Weather Service transmits an alert tone to activate commonly available weather alert receivers to warn of impending severe and potentially life threatening weather such as tornados, thunderstorms, floods and blizzards. Known receivers can be set to issue a siren, flash an LED and/or announce the voice weather alert message in response to receiving and decoding an alert tone.
All of these alert receivers suffer from the major operational defect of the listener missing the alert message if the listener is away from the receiver when the alert is issued. If the flashing LED is seen, or the siren is heard, by the listener some time after the alert message is broadcast, the listener will have to take critical time and effort to determine the time and contents of the alert message.
The instant invention solves these problems by automatically recording the alert message, and the day and time the alert message was received, into solid state voice storage circuitry into the alert receiver. The listener is able to immediately playback the alert message upon returning to the alert receiver and will hear the day and time the alert message was received.
Most alert receivers are tuned for a specific radio channel and require special receivers. Therefore, another defect in present alerting systems is that they require listeners to individually obtain special equipment to receive the alerts of different agencies. Many listeners will not go to the time and expense of obtaining the necessary receivers and many listeners will not find it feasible to carry this equipment with them as they travel. The instant invention solves these problems by receiving and recording the alert message received on one radio channel and relaying the alert message, or an alert receiver generated alarm tone, on other communication systems, while not interfering with communication in progress on the other communication system.
A number of alert receivers, and specifically alert receivers for receiving weather alerts, have a manual switch which permits the listener to choose one radio channel to monitor from a number of preselected radio channels. For example, the National Weather Service broadcasts weather information and warning on seven different radio channels from transmitters located around the country. These alert receivers are unacceptable for mobile use as the user must manually listen to each possible radio channel and choose which radio channel to monitor. This selection cannot be safely accomplished by the driver-of the vehicle while the vehicle is in motion. Furthermore, as the vehicle moves from one location to another, and in and out of the radio signal coverage areas of the various transmitters, these alert receivers need to be manually retuned. Since the weather is continuously broadcast and is extremely tedious to listen to for more than a few minutes, most users keep the speaker muted the majority of the time. If the speaker is muted, the listener will not know that the alert receiver is out of range of a transmitter and a critical alert can easily be missed.
A number of recently manufactured scanners have a weather scan function. Pressing the weather scan button scans the seven preprogrammed weather channels and the scanner stops on the first channel on which a radio signal is received. There are a number of problems with this scan function. As stated above, the listener must press the button to start the scan sequence. If the listener is mobile, the listener will have to remember to periodically press the scan button as the vehicle moves in and out of the transmission coverage area of the various transmitters. These scanners do not have an alert feature, an alert message record feature or a day and time stamp feature, all of which are important aspects of the instant invention.
In areas with overlapping radio coverage from a number of different radio transmitters on different channels, the instant invention's scan function will automatically choose the strongest received radio signal having modulated audio. In this manner, if the normally strongest transmitter fails or if the strongest transmitter loses its modulated audio, for a preset period of time such as for thirty seconds, the instant invention's scan function will automatically seek the best backup channel, if one is available. The instant invention's scan function will also periodically monitor all of the preselected channels, at preset time intervals, such as every twenty minutes, to determine if the strongest channel has returned to service.
A common problem with alert receivers is that a number of alerts broadcast on one radio channel might not be of interest to listeners to the alert receiver or on other communication systems linked to the alert receiver. To solve this problem, the instant invention allows the user of the alert receiver to program a digital code into the alert receiver so that the alert receiver only triggers in response to specific digital codes broadcast on the monitored radio channel.
Another common problem with alert receivers is that they are usually limited to monitor one preselected radio channel and to detect a few preset alert tones on the preselected radio channel. The instant invention solves this problem by utilizing frequency synthesized technology for both selecting the radio channel to be monitored as well as the alert tone(s) to be detected.